CHARGING ENERGY STORAGE UNITS OF A VEHICLE AT WEAK ENERGY SUPPLY SYSTEMS

An on-board power subsystem has an energy storage unit and a control device for charging the energy storage unit, as well as an on-board power connection for connection to electrical components of the vehicle, and a DC voltage connection for connection to a land-based charging station and an energy subsystem. A switching device is arranged between the on-board power connection and the energy subsystem, and a charger is arranged between the energy storage unit and the energy subsystem. The on-board power subsystem has at least one power converter connected on the AC voltage side to the energy subsystem and operable both as an AC/DC converter and as a DC/DC converter. The control device can operate the energy subsystem as a DC voltage grid during the charging process and as an AC voltage grid during independent operation of the vehicle.